Method of removing trim from patterns

ABSTRACT

A pattern is scored in a major surface of a piece of flat glass, and the score is propagated into a fracture that extends at least almost entirely to an opposite major surface of the piece. Heat is applied at a location adjacent to an edge of the piece until a red glow is visible at the glass surface. At that time, an edge nick is applied to the glass adjacent to the red glow to complete a vent from the edge nick to the fracture defining the pattern. This is repeated several times to free the pattern from its trim without damaging the edge of the pattern.

United States Patent 1 1 De Torre Sept. 4, 1973 [54] METHOD OF REMOVINGTRIM FROM 2,169,687 8/l939 Fowler et al 225/9o.5 PATTERNS, 2,584,8512/1952 Dunipace 225 2 3,474,944 10/1969 Chatelain et aI .1 225/93.5 X

[75] Inventor: Robert P. De Torre, Pittsburgh, Pa.

[73] Assignee: PPG Industries, Inc., Pittsburgh, Pa. PrimaryExaminerFrank T. Yost Filed: p 28, 1972 AttorneyRussell A. Eberly 21 Al. N 248 468 1 pp 0 57 ABSTRACT Related US. Application Data [63]Continuation-inart of Ser Nos 57 574 Jul 23 A pattern ls scored "3 amajor surface of a plece of flat 1970 abandon: and Ser 68'735'se lglass, and the score 15 propagated mm a fracture that abamloned and NoM5 1 extends at least almost entirely to an opposite major surface ofthe piece. Heat is applied at a location adja- 52 U.S. c1 225/2 65/113225/935 cent to an edge Piece red glow is visible 51 Int. 01...; 1526f3/06 at the glass shrfacethat time an edge hick is P- 58 Field of Search225/2 93.5- 82/12- P the glass adjacent the red 810W Complete 30/16495.6512 1 a vent from the edge nick to the fracture defining the pattern.This is repeated several times to free the pat- 56] References Citedtern from its trim without damaging the edge of the pat- UNITED STATESPATENTS 1,738,228 12/1929 Campbell et al 225/2 27 Claims, 13 DrawingFigures SCORING A PATTERN IN A PIECE OF FLAT GLASS MECHANICALLY TAPF'INGBENEATI-I THE SCORE (OPTIONAL STEP) APPLYING HEAT ALONG THE ENTIRE SCOREFROM ABOVE TO PROPAGATE THE SCORE BUT LEAVE A SKIN REMAINING APPLYINGHEAT ALONG THE SCORE FROM BELOW (OPTIONAL STEP) APPLYING AN EDGE NICK TOTHE FLAT GLASS BREAKOUT SEAMING UPPER AND LOWER PORTIONS OF THE PATTERNEDGES PATENTEI] E 4 7 sum 1 or 4 SCORING A PATTERN IN A PIECE OF FLATGLASS SCORE FROM ABOVE TO PROPAGATE THE APPLYING HEAT ALONG THE ENTIRE 7SCORE BUT LEAVE A SKIN-REMAINING FROM BELOW (OPTIONAL STEP) APPLYINGHEAT ALONG THE SCORE APPLYING SPOT HEAT TO A MAJOR SURFACE OF THE PIECEADJACENT TO AN EDGE UNTILA RED GLOW APPEARS APPLYING AN EDGE NICK TO THEFLAT GLASS I BREAKOUT PATENTEDSEP 4m: I 3756482 I saw 20F 4 PATENTEDSEPM975 SCORING A, PATTERN IN A PIECE OF FLAT GLASS TOP CENTER TAPPING TOPROPAGATE THE SCORE INTO A FRACTURE APPLYING HEAT ALONG THE FRACTUREAPPLYING HEAT ALONG THE FRACTURE FROM BELOW TO FURTHER PROPAGATETHE'FRACTURE BUT LEAVING A THIN SKIN REMAINGQOPTIONAL STEP) APPLYINGSPOT HEAT TOA MAJOR SURFACE OFTHE PIECE ADJACENT TO AN EDGE UNTIL A REDGLOW APPEARS APPLYING AN EDGE NICK TO THE FLAT GLASS BREAKOUT FIGJZPORTIONS OF THE PATTERN EDGES' 1 METHOD OF REMOVING TRIM FROM PATTERNSCROSS REFERENCE TO RELATED APPLICATIONS BACKGROUND OF THE INVENTION 1.Field of the Invention This invention relates to a method for cuttingglass,

and in particular, for the removal of glass trim from a pattern by athermo-mechanical means without damaging the edge or edges of thepattern.

2. Description of the Prior Art In the manufacture of glass patterns, ithas hitherto been customary to place a score in the form of the patternon a piece of flat glass and apply a mechanical bending moment about thescore to separate the trim from the pattern. In this connection,reference may be made to Sherts, U. S. Pat. No. 1,887,564; Echter etal., U. S. Pat. No. 2,508,017; and Augustin et al., U. S. Pat No.3,520,456. This procedure is disadvantageous because it causes edgedamage (chipping of the bottom corner), which necessitates grinding andpolishing.

It has been suggested that heat may be applied adjacent to a score toseparate the trim from a pattern. In this connection, reference may bemade to Chatelain et al., U. S. Pat. No. 3,474,944. However, the use ofa thermal means alone requires. a substantial amount of time to run avent. In addition, if this vent is started adjacent to a score, the ventcontacts the pattern with extreme violence, often causing chipping.Further, there is an increased possibility that the vent will cross thescore and damage the pattern since the vent has more momentum at itsconception.

SUMMARY OF THE INVENTION According to an embodiment of the presentinvention, grinding to size and edge polishing, in the preparation ofglass patterns, areadvantageously avoided by use of a procedure thatinvolves: (l) scoring a major surface of a piece of flat glass in theform of a pattern; (2) propagating the score into a fracture thatextends at least almost entirely to an opposite major surface of thepiece of glass; (3) heating the glass on the scored surface within aboutone inch of the edge of the piece until a red glow is visible on thesurface; (4) applying a mechanical defect, such as an edge nick, to theedge of the piece adjacent to the red glow to create a vent from theedge to the fracture; and (5).repeating the heating and the applying ofdefects at various locations on the piece to complete a plurality ofvents and "breakout or separate the trim from the pattern.

According to an alternate embodiment of the present invention, edgenicks are applied to the piece of glass before the glass is heated. Inthis embodiment, heatis applied adjacent to the edge nicks after theyare made.

When removing a pattern from a piece of flat glass, it is possible todamage the pattern edges in the scoring operation, the fracturepropagation, or the breakout. If the piece of glass is less thanapproximately millimeters thick, a conventional score may be applied tothe glass, followed by heat to propagate the score into a fracture thatruns along the score at least almost entirely to the opposite majorsurface of the piece of glass without damaging the pattern edges. Whenremoving a pattern from a piece of glass that is thicker thanapproximately lO millimeters thick, it is advantageous to use thedeep-scoring techniques taught in Belgian Patent No. 770,316, to insurethat the edges of the pattern are not damaged during scoring or fracturepropagation. To understand why this is so, one must realize that themajor surfaces of a piece of flat glass are normally in compression withthe central zone therebetween in tension. As the glass is heated, thecenter tension increases until it reaches at least approximately 1000pounds per square inch and then the glass fails. If there is a score ona major surface of the piece of glass, and the glass is heated along thescore, the resulting propagation will follow the score only if the scoreis deep enough to approach the zone of center tension and steer thefracture. With glass that is less than approximately 10 millimeters inthickness, a conventional score will penetrate the glass sufficiently tosteer the fracture. With glass thicker than this, a conventional scorewill not penetrate the tension zone unless scoring pressures are so highas to crush the glass. The trick,-

therefore, is to get a score that is deep enough to penetrate thetension zone, without crushingthe edge. A method and apparatus forperforming this function is taught in the above-mentioned BelgianPatent.

The present invention prevents edge damage during breakout or separationof the trim from the pattern. It requires that a fracture (defining apattern) extends between most of the thickness of the piece of glass sothat the fracture will act as a dam to stop a vent from traveling intothe pattern when it is freed from the trim. While the breakout method ofthe present invention will separate a pattern from a trim without initself damaging the pattern edge, if the scoring techniques describedabove are not practiced, such that the pattern edges are damaged beforethe pattern is separated from the trim, the breakout method of thepresent invention cannot improve the edge. For this reason, deep-scoringtechniques are normally used in combination with the breakout method ofthe present invention for thicker glass.

In accordance with the present invention, it is possible to remove trimsfrom glass patterns while minimizing wastage of glass.

Further, inaccordance with the present invention, it is possible toremove trims from glass patterns without damaging the edges of thepattern, so that only light seaming of the edges is required.

. Further, in accordance with the present invention, it is now possibleto remove a trim from a glass pattern leaving edges on the patternthat'are smooth, strong, accurate and perpendicular to the majorsurfaces of the piece.

DESCRIPTION OF THE DRAWINGS A complete understanding of the inventionmay be obtained from the foregoing and following description thereof,taken together with the appended drawings, which are not drawn to scaleunless noted, in which:

FIG. 1 is a flow diagram of a process showing all steps thereofincluding both essential and optional steps in accordance with thepresent invention;

FIG. 2 is a vertical cross-sectional view of a typical cutting wheelused in the practice of the present invention;

FIG. 3 is a perspective view of a typical set-up for scoring circles inaccordance with the present invention;

FIG. 4 is a perspective view of a jet heat source directing heat along apreviously formed score line;

FIG. 5 is a top view of a glass surface with a circular pattern;

FIG. 6 is a top view of the surface of FIG. 5, after three vents havebeen created;

FIG. 7 is a top view of the glass in FIG. 6, after the pattern has beenreleased from the trim;

FIG. 8 is a top view of a glass surface illustrating a layout of aplurality of patterns;

FIG. 9 is a top view of the glass surface in FIG. 8 after several ventshave been completed;

FIG. 10 is a top view of the glass in FIG. 9, after the patterns havebeen released from the trim;

FIG. 11 is an elevation view (drawn to scale except for the bottom edgeof the fissure which is diagrammatic) of an edge of a piece of glass cutin accordance with the instant invention;

FIG. 12 is a flow diagram of a process showing all steps thereofincluding both essential and optional steps in accordance with anadditional embodiment of the present invention; and

FIG. 13 is a perspective view of a tool used to top center tap.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, a flowdiagram of a process in accordance with the present invention is shown.The scoring step of block 16 in the flow diagram of FIG. 1 may be eitherconventional scoring or deep-fissure scoring. With thinner glass, suchas below approximately 10 millimeters in thickness, a conventional scoresuffices, though a deeper score can be used. With thicker glass, it isnecessary to use deep-scoring techniques if the fracture is to followthe score.

Referring to FIG. 2, there is shown a cutting or scoring wheel 4 made oftungsten carbide or other suitable material of hardness of about 7 ormore on Mohs scale. For pieces of flat glass less than approximately 10millimeters in thickness, a conventional wheel may be used, but it ispreferred that it be blunt, such as about 160. For pieces of flat glassgreater than about 10 millimeters in thickness, the wheel should beconstructed in accordance with the dimensions and characteristics setforth in Belgian Patent No. 770,316. Said patent states that the wheelshould. have a radius between approximately 6 to approximately 25millimeters, and preferably between 9 and 16 millimeters. The baseangle, i.e., the angle between the two sides 6 and 8, if extended, isabout l20and the angle between the sides 10 and 12 (the cutting angle)is between about 150 and about 165, with 160 providing optimum results.The wheel has a central axle hole 14 which may have a diameter of about2.4 millimeters. Hole 14 provides a means for rotatably mounting saidwheel on a shaft that is passed through the axle hole 14.

Referring to FIG. 3, there is shown a typical set-up for scoring thecircumference of a pattern P, such as a circle, on a piece of flat glassG in accordance with the present invention. The glass is placed on acutting table 60 with a suitable template 62 mounted on the cuttingtable. Pneumatic means (not shown) may be used to supply force to thecutting tool 64. While a hand-held cutting tool 64 has been illustrated,it will be obvious to one skilled in the art that there are manycommercially available means for housing the scoring wheel 4 andsupplying a suitable scoring force.

Referring now to the block 18 of FIG. I, there is indicated a step ofmechanically tapping a portion of the score. This is done with a hammeror mallet, gently, from beneath the glass on the face opposite the scoreat one point of the score. The purpose of this operation is merely tostart the opening to a considerable depth of the score and therebydiminish the capacity requirement of the thermal source to be used atthe beginning of the immediately succeeding operation (block 20). Thestep of block 18 can be omitted entirely provided that dwell time of theheating process is increased to start the propagation of the deepfissure by mechanically tapping the glass before the heating process(block 20), about 10 to 15 seconds dwell time in 18- millimeter glassare saved.

Referring now to block 20, the next step of the process comprisesapplying heat along the score from the top and progressively along it tonearly open it. This may be done with a small hand-held blowtorch or thelike. Various kinds of hand-held torches that burn propane or othersuitable gaseous fuel are readily available and are familiar to thoseskilled in the art; these may be used. Other alternatives will suggestthemselves to persons of ordinary skill in the art, such as the use of aflameless, electrically operated serpentine gas heater, producing an airflow of approximately 35 cubic feet per hour at an outlet temperature ofapproximately 1750F. with a power utilization of approximately 470watts. The rate of passage of the heating means with respect to thescore along its length should depend, to some extent, upon the thermaloutput of the source and the thickness of the glass. It will probably besubstantially slower than the rate of passage of the scoring apparatus.Since the speed of scoring is not critical, it is usually high (about 25centimeters per second). The heat source generally proceeds along thescore at about 5-l2 centimeters per second. The operator can tellwhether the rate of the passage used is satisfactory; as the heat sourceis moved along, the advancing front of the area that has been thermallyopened in accordance with this step of the invention can be seen toprecede the location of the source by approximately 20 to 60millimeters. It is to be understood that the thermal opening that ispracticed in accordance with this step of the invention does not usuallycause the edge to be severed from the glass instantaneously. In the caseof glass 18 to 19 millimeters thick, approximately I to 2 millimeters ofglass usually remains unsevered at the bottom of the piece.

Referring to FIG. 4, there is shown a small, hand-held gas torch F witha flame 31 directed toward score 34. As the torch F is moved along score34, in the direction of arrow A, a fracture 36 is propagated in adirection perpendicular to the major glass surface 40, leaving only athin skin 38 holding the trim to the pattern. In the case of the use ofa small hand-held gas torch, the flame should be directed at an angle of20 to with respect to a major surface of the glass.

Referring to block 22, it is desirable, when higher quality cuts aredesired, to pass a torch underneath the intended line of cut and alongits entire length, taking for example, something like 7 to 15 seconds totraverse a length of 5 to 6 meters. This further reduces the thicknessof skin 38 to aid in obtaining a cut of even higher quality. When thisstep is used, it must follow after, and not before, the top heating ofthe score or no benefit is obtained.

When removing a pattern, such as a circle or an oval, from a piece offlat glass, one is not likely to get a smooth edge by supporting thescore and snapping the bottom skin, as is done when producing straightedges using the practice of deep scoring and then heatpropagating thescore to near fracture.

Referring to block 24 of FIG. 1, heat is preferably applied to thescored surface adjacent to an edge of the piece by holding a heatsource, such as a gas flame, within approximately one inch of the glassedge until a hot spot is created on the glass surface, as indicated by ared glow. FIG. 5 shows the piece of glass G with a pattern P that hasbeen produced by the process described hereinabove. Heat may be applied,for example, to the trim of a piece of flat glass, 19 millimeters inch)thick, at a location that is approximately 25 millimeters (approximately1 inch) from the glass edge, by a torch with a 38-millimeter (Hi-inch)propane flame for about 7 to 10 seconds to create a hot spot 75 having asurface temperature of approximately 1000F., as indicated by a red glow.Referring to block 26 of FIG. 1, an edge nick 70 is then applied to thepiece G adjacent to the red glow to run a vent, such as the oneillustrated in FIG. 6 at 76, from the edge to the pattern P. It ispossible to create vents without any nicks by merely heating the glassuntil sufficient tensile stresses develop to cause a fracture. This is aslow process and disadvantageous since the vent often strikes thepattern with extreme violence, causing edge damage.

If the operator continues to create vents, one at a time, from the edgesof the piece G to the pattern P, eventually the scrap or trim T willseparate from the finished pattern P. The trim T breaks free of thepattern P in a rather dramatic fashion, which is referred to in block 28of FIG. 1 and throughout this disclosure as breakout.

The phenomenon of breakout occurs because the interior edge 90 of trim Ttends to be of greater length than the exterior edge of the pattern P.This is because the trim has been heated to create the hot spots. Theheating of the glass along score 34 (blocks 20 and/or 22 of FIG. 1) alsostretches the interior trim edge 90 more than the exterior edge of thepattern P, even though the heat is applied along the score 34. This isdue to the relatively low mass of the trim T with respect to the patternP, thus causing the trim T to get hotter than pattern P and thereforeexpand by a greater amount. It should be kept in mind that while theheating steps of blocks 20 and 22 aid in breakout," the presentinvention is not limited to these steps since the heat placed in theglass when the hot spots are created is sufficient to producesatisfactory breakout. Trim edge 90 tends to separate from the exterioredge of pattern P as soon as the first hot spot is created, but it isnot until a sufficient number of vents are created that the pattern Pisreleased from the trim T.

FIG. 6 shows the piece of glass G after vents 76, 76'

, and 76" have been created. It should be understood that it is unlikelythat one could actually view'the glass in such a state, since breakout"would almost certainly occur with three vents placed as shown. If vent76 is omitted and vent 76" is created immediately after vent 76,breakout" will usually occur with upper portion 92 separating from lowerportion 94. It is more advantageous to create vents successively about apattern to minimize the possibility of large portions of trim separatingfrom a pattern. Therefore, for best results, vent 76 should be createdfirst; then vent 76; and then vent 76". This minimizes the violenceduring the separation and reduces or eliminates the edge chipping causedthereby.

Referring to FIG. 7, there is shown a top view of the pattern P after ithas been freed from trim T. The number of vents necessary for breakout"depends on the complexity of the pattern. When removing a circularpattern from a rectangular piece of glass, two vents may be sufficient,but as pointed out hereinabove, three vents are preferred. It isdifficult to say how soon the edge nick must be applied, but as long asthe edge nick is applied while the red glow remains, a vent will runwith no problems. I-Ieat increases the tensile stresses in the glass,and the red glow on the glass surface indicates that these stresses arehigh enough that an edge nick adjacent to the red glow will cause atensile failure or vent.

Referring to FIG. 8, there is shown a view of the top major surface 40of a piece of flat glass G, illustrating a layout of circular patterns Pthat has proven to be very convenient. The dimensions of the glass G maybe such that each side of the piece is twice the diameter of the circlesto be cut plus approximately 6.5 centimeters (2.5 inches). FIG. 8 showsa center nick 72 between the four circular patterns P. This center nick72 is helpful where more than one pattern is to be removed from a piece.Heat may be applied adjacent to the center 73 of nick 72 to create vents74 between the patterns P, as shown in FIG. 9. Vents 76 are then createdfrom the edges of the piece to the patterns P, as described hereinabove.As is the case with the glass illustratedin FIG. 6, it is unlikely thatone would ever see a view such as the one illustrated in FIG. 9, sincebreakout would almost certainly occur with twelve vents 76. FIG. 10shows the circular patterns P after they have been released from thetrim.

It should be kept in mind that the present invention relates to removingall patterns from pieces of flat glass, and the circles illustrated aremerely exemplary. Further, while there has been illustrated convenientlocations for hot spots and edge nicks, these locations may be movedalong the edge of the glass, if desired.

It is also possible to apply the edge nicks to the piece of glass beforeheat isapplied. This will usually result in a pattern with edges of aquality that is equal to those produced by heating before edge nicking.However, the separation when edge nicking is done first is more violentthan when heating is done first, and sometimes,

with the former, there is contact between the edges of the pattern andthe trim, causing damage. This is an infrequent occurrence, and thepresent process of separating a pattern from its trim is more desirablethan those of the prior art, even if the edge nicks are applied beforethe heating. But, it is even more desirable to heat and then edge nick.

At this point, there may be conducted an inspection to determine thequality of the cut that has been opened. In the inspection along the cutedge, looking perpendicularly to the edge, it is customary to see apattern such as that indicated in FIG. 11. The top surface of the glassis there designated with the numeral 40, and a short distancetherebeneath is seen a marking 50 that has the appearance of a series offine serrations and is indicative of the extent of the score caused bythe penetration of the cutting wheel into the glass. In the case of adeep fissure, the marking 50 in glass 18 to 19 millimeters thick is atleast 1.75 millimeters from the top surface of the glass. Normally, theregion between surface 40 and marking 50 includes approximately 6percent to 30 percent of the thickness of the glass. From the marking 50to a faint line 58 there is a region 52 that is a smooth, planarfracture and, in the case of glass 18 to 19 millimeters thick, extendsfrom the marking 50 for something like to 17 millimeters of thethickness of the glass down its severed edge. Region 52 extends throughthe glass for about 60 to 90 percent of its thickness in a directionsubstantially perpendicular to the glass surfaces 40 and 56. Below thatis a region 54 that is relatively unmarked and extends from a faint line58 to the bottom surface 56 of the glass. Faint line 58 is substantiallyparallel to the bottom surface 56 and is spaced therefrom byapproximately 0.5 to approximately 2 millimeters and indicates theextent to which the fracture in the glass penetrates when it isthermally opened as taught hereinabove. The distance between line 58 andsurface 56 corresponds to about 3 percent to about [0 percent of thethickness of the glass. Of course, the dimensions indicated above willvary somewhat with glass pieces of different thickness, but the generalarrangement and relationship remains the same.

As used in this application, the terms deep fissure, fissure, deep scoreor score" refer to the area between surface 40 and marking 50. The termfracture" can refer to the area between marking 50 and line 58, and, inthe relatively few instances where heat propagates the fracture throughto the bottom surface of the glass, it can refer to the area betweenmarking 50 and the bottom surface 56 (there is no line 58 under thiscircumstance). When used broadly, fracture includes both of thesesituations.

As a final step, indicated in block of FIG. 1, there is conducted alight seaming of only the upper and lower portions of the edges of thepattern being cut. This leaves a smooth edge with no evidence of marking50 or line 58 remaining. There may be used, for example, a hand-heldbelt sander using a belt 75 millimeters wide by 600 millimeters long.This is a conventional operation, and it does not require furtherelaboration or explanation.

The result is that there is produced a finished piece of glass thatcompares favorably in its edge strength to similar pieces produced bythe prior-art method of rough cutting, mechanical snapping, grinding tosize, and then polishing. The pieces of the present invention have edgestrength of about 4.35 to 4.63 kilograms per square centimeter in theconventional beam-loading test, in comparison with strengths such as4.63 to 4.91 kilograms per square centimeter for the prior-artground-and-polished pieces. Either will meet specifications on'customaryglazing installations. In achieving the edge-strength values indicatedabove, the final seaming operation is important. Without the finalseaming operation, the edge strength is on the order of 3.27 to 3.60kilograms per square centimeter.

Referring to FIG. 12, there is shown a flow diagram of a process usedfor removing patterns from flat glass in accordance with an additionalembodiment of the present invention. The additional embodiment differsfrom the one hereinabove described by the manner in which the score ispropagated. Accordingly, only the differences between the twoembodiments will be set forth in great detail.

The scoring step of block 16' of FIG. 12 is identical to the scoringstep of block 16 of FIG. 1. The apparatus shown in FIGS. 2 and 3 isequally applicable to the second embodiment. I

Referring to block 18' of FIG. 12, this step is similar to the step ofblock 18 of FIG. 1. In block 18 of FIG. 1, a mechanical tap from beneatha portion of the score is used to commence propagation of a fracture.According to the second embodiment, it has been discovered that byapplying the tap from above at approximately the center of curvature ofa curved score, a fracture not only propagates to a greater depth as inthe case ofa tap beneath the score (block 18), but further, a tap at thecenter of curvature of the curved score propagates the fracture aroundthe entire circumference of the curved score. It is important to pointout that the mechanical tapping step of block 18 is not a critical partof the first-described embodiment. It merely reduces dwell time with theheat torch. However, the top center tapping of block 18' of theseconddescribed embodiment is an essential part of this embodiment,since it eliminates the necessity of top heating (block 20') except whenedges of extremely high quality are desired, and it is faster to apply afirm tap to the approximate center of curvature of a curved score thanto heat around the entire circumference. In other words, if the topcenter tap is omitted, one can use heat to propagate a fracture as inthe first embodiment, but heating along a score is slower than topcenter tapping.

Referring to FIG. 13, there is shown a tool that may be used in thecenter tap step of block 18'. The tool is placed at the approximatecenter of curvature of the curved score with portion 84 resting directlyon the glass. The operator strikes the tool 80 at 82 from above with ahammer or mallet.

Referring to block 20' of FIG. 12, the next step may be to apply heatalong the deep fissure from above to propagate the fracture. This issimilar to the step recited in block 20 of FIG. 1.. As pointed outabove, step 20' is not essential in propagating the score into afracture unless extremely high quality edges are desired, but it doesaid in breakout" since it supplies heat which helps to increase thelength of the interior edge of the trim.

Referring to block 22' of FIG. 12, heat is applied along the fracturefrom below to propagate the fracture and leave a thinner skin. This stepis similar to the heating of block 22 of FIG. 1 in that it conditionsthe glass for breakout by further propagating the fracture. As above,this step is not an essential part of the fracture propagation unlessextremely high quality edges are desired, but it aids in the breakout.

The steps of blocks 24, 26, 28' and 30' of FIG. 12 are identical tothose described in connection with blocks 24, 26, 28 and 30 of FIG. 1and a further description of these blocks is therefore deemedunnecessary.

Having now fully disclosed the invention, what I claim is as follows:

I claim as my invention:

1. A method of severing a trim from a pattern in a piece of flat glasscomprising the steps of:

a. producing a fracture in the form of the pattern in the piece of flatglass,

b. creating a first vent from an edge of said piece to said fracture byheating an area of said trim and applying a mechanical defect to saidedge adjacent to said area, and

c. creating additional vents to separate the trim from the pattern.

2. A method as set forth in claim 1, further characterized in that saidfirst vent is created by:

a. heating said trim on a major surface thereof to create a hot spot,and

b. applying said mechanical defect to said edge of said piece adjacentto said hot spot to complete said vent from said edge of said piece tosaid fracture.

3. A method as set forth in claim 2, further characterized in that saiddefect is an edge nick.

4. A method as set forth in claim 3, further characterized in that saidtrim is heated within approximately 25 millimeters of the edge.

5. A method as set forth in claim 2, further characterized in that saidadditional vents are each created by heating said trim on a majorsurface thereof to create a hot spot and applying a mechanical defect toan edge of said piece adjacent to said hot spot to complete said ventfrom the edge of said piece to the fracture.

6. A method as set forth in claim 2, further characterized in that saidadditional vents are each created by applying a mechanical defect tosaid edge of said piece, and heating said trim on a major surfacethereof adjacent to said mechanical defect to complete a vent from saidedge of said piece to said fracture.

7. A method as set forth in claim 2, further characterized in that saidvents are created one at a time.-

8. A method as set forth in claim 7, further characterized in that saidpattern is in the form of a circle.

'9. A method as set forth in claim 7, further characterized in that aplurality of patterns are removed from a single piece of glass. I

10. A method as set forth in claim 9, further including the step of:

a. creating additional vents between the patterns.

11. A method as set forth in claim 10, further characterized in thatsaid additional vents are created by:

a. applying nicks in one of the major surfaces of the piece between thepatterns, and I b. heating said nicks to create vents between thepatterns.

12. A method as set forth in claim 11, further characterized in thatsaid fracture is produced by the steps of:

a. scoring a major surface of the piece in the form of the pattern, and

b. propagating said score into a fracture that extends at least almostentirely to an opposite major surface of said piece.

13.- A method as set forth in claim 1, further characterized in thatsaid first vent is created by:

a. applying said mechanical defect to said edge of said piece, and

b. heating said trim on a major surface thereof adjacent to saidmechanical defect to complete a vent from said edge of said piece tosaid fracture.

14. A method as set forth in claim 13, further characterized in thatsaid defect is an edge nick.

15. A method as set forth in claim 14, further characterized in thatsaid trim is heated within approximately 25 millimeters of the edge.

16. A method as set forth in claim 13, further characterized in thatsaid additional vents are each created by heating said trim on a majorsurface thereof to create a hot spot and applying a mechanical defect toan edge of said piece adjacent to said hot spot to complete said ventfrom the edge of said piece to the fracture.

17. A method as set forth in claim 13, further characterized in thatsaid additional vents are each created by applying a mechanical defectto said edge of said piece, and heating said trim on a major surfacethereof adjacent to said mechanical defect to complete a vent from saidedge of said piece to said fracture.

18. A method as set forth in claim 13, further characterized in thatsaid vents are created one at a time.

19. A method as set forth in claim 18, further characterized in thatsaid pattern is in the form of a circle.

20. A method as set forth in claim 18, further characterized in that aplurality of patterns are removed from a single piece of glass.

21. A method as set forth in claim 20, further including the step of:

a. creating additional vents between the patterns.

22. A method as set forth in claim 21, further characterized in thatsaid additional vents are created by:

a. applying nicks in one of the major surfaces of the piece between thepatterns, and

b. heating said nicks to create vents between the patterns.

23. A method as set forth in claim 22, further characterized in thatsaid fracture is produced by the steps of:

a. scoring a major surface of the piece in the form of the pattern, and

b. propagating said score into a fracture that extends at least almostentirely to an opposite major surface of said piece.

24. A method of severing a trim from apattern in a piece of flat glasscomprising the steps of:

a. scoring a major surface of said piece in the form of said pattern,

b. tapping said score from below to start a fracture,

c. applying heat along said score from above to propagate said scoreinto a fracture that extends at least almost entirely to an oppositemajor surface of said piece,

d. applying heat along said score from below,

e. applyingspot heat to a major surface of said trim adjacent to an edgeof said piece until a red glow appears,

f. applying a mechanical defect to-said edge of said piece adjacent tosaid red glow to complete a vent from said edge of said piece to saidfracture,

g. creating additional vents in said trim until said trim is separatedfrom said pattern, and

h. seaming upper and lower portions of the pattern edge.

25. A method of severing a trim from a pattern in a piece of flat glasscomprising the steps of:

a. scoring a major surface of said piece in the form of said pattern,

b. tapping said score from below to start a fracture,

c. applying heat along said score from above to propagate said scoreinto a fracture that extends at least almost entirely to an oppositemajor surface of said piece,

d. applying heat along said score from below,

e. applying a mechanical defect to said edge of said piece,

f. heating said trim on a major surface thereof adjacent to saidmechanical defect to complete a vent from said edge of said piece tosaid fracture,

g. creating additional vents in said trim until said trim is separatedfrom said pattern, and

h. seaming upper and lower portions of the pattern edge.

26. A method of severing a trim from a pattern in a piece of flat glasscomprising the steps of:

a. scoring a major surface of said piece in the form of said pattern,

b. applying a top center tap at the approximate center of curvature ofsaid pattern to propagate the score into a fracture,

c. applying heat along the fracture from above to further propagate thefracture,

d. applying heat from below along the fracture to further propagate thefracture,

e. applying spot heat to a major surface of said trim adjacent to anedge of said piece until a red glow appears,

f. applying a mechanical defect to said edge of said piece adjacent tosaid red glow to complete a vent from said edge of said piece to saidfracture,

g. creating additional vents in said trim until said trim is separatedfrom said pattern, and

h. seaming upper and lower portions of the pattern edge.

27. A method of severing a trim from a pattern in a piece of flatglasscomprising the steps of:

a. scoring a major surface of said piece in the form of said pattern,

b. applying a top center tap at the approximate center of curvature ofsaid pattern to propagate the score into a fracture,

c. applying heat along the fracture from above to further propagate thefracture,

d. applying heat from below along the fracture to further propagate thefracture,

e. applying a mechanical defect to said edge of said piece,

f. heating said trim on a major surface thereof adjacent to saidmechanical defect to complete a vent from said edge of said piece tosaid fracture,

g. creating additional vents in said trim until said trim is separatedfrom said pattern, and

h. seaming upper and lower portions of the pattern edge.

1. A method of severing a trim from a pattern in a piece of flat glasscomprising the steps of: a. producing a fracture in the form of thepattern in the piece of flat glass, b. creating a first vent from anedge of said piece to said fracture by heating an area of said trim andapplying a mechanical defect to said edge adjacent to said area, and c.creating additional vents to separate the trim from the pattern.
 2. Amethod as set forth in claim 1, further characterized in that said firstvent is created by: a. heating said trim on a major surface thereof tocreate a hot spot, and b. applying said mechanical defect to said edgeof said piece adjacent to said hot spot to complete said vent from saidedge of said piece to said fracture.
 3. A method as set forth in claim2, further characterized in that said defect is an edge nick.
 4. Amethod as set forth in claim 3, further characterized in that said trimis heated within approximately 25 millimeters of the edge.
 5. A methodas set forth in claim 2, further characterized in that said additionalvents are each created by heating said trim on a major surface thereofto create a hot spot and applying a mechanical defect to an edge of saidpiece adjacent to said hot spot to complete said vent from the edge ofsaid piece to the fracture.
 6. A method as set forth in claim 2, furthercharacterized in that said additional vents are each created by applyinga mechanical defect to said edge of said piece, and heating said trim ona major surface thereof adjacent to said mechanical defect to complete avent from said edge of said piece to said fracture.
 7. A method as setforth in claim 2, further characterized in that said vents are createdone at a time.
 8. A method as set forth in claim 7, furthercharacterized in that said pattern is in the form of a circle.
 9. Amethod as set forth in claim 7, further characterized in that aplurality of patterns are removed from a single piece of glass.
 10. Amethod as set forth in claim 9, further including the step of: a.creating additional vents between the patterns.
 11. A method as setforth in claim 10, further characterized in that said additional ventsare created by: a. applying nicks in one of the major surfaces of thepiece between the patterns, and b. heating said nicks to creaTe ventsbetween the patterns.
 12. A method as set forth in claim 11, furthercharacterized in that said fracture is produced by the steps of: a.scoring a major surface of the piece in the form of the pattern, and b.propagating said score into a fracture that extends at least almostentirely to an opposite major surface of said piece.
 13. A method as setforth in claim 1, further characterized in that said first vent iscreated by: a. applying said mechanical defect to said edge of saidpiece, and b. heating said trim on a major surface thereof adjacent tosaid mechanical defect to complete a vent from said edge of said pieceto said fracture.
 14. A method as set forth in claim 13, furthercharacterized in that said defect is an edge nick.
 15. A method as setforth in claim 14, further characterized in that said trim is heatedwithin approximately 25 millimeters of the edge.
 16. A method as setforth in claim 13, further characterized in that said additional ventsare each created by heating said trim on a major surface thereof tocreate a hot spot and applying a mechanical defect to an edge of saidpiece adjacent to said hot spot to complete said vent from the edge ofsaid piece to the fracture.
 17. A method as set forth in claim 13,further characterized in that said additional vents are each created byapplying a mechanical defect to said edge of said piece, and heatingsaid trim on a major surface thereof adjacent to said mechanical defectto complete a vent from said edge of said piece to said fracture.
 18. Amethod as set forth in claim 13, further characterized in that saidvents are created one at a time.
 19. A method as set forth in claim 18,further characterized in that said pattern is in the form of a circle.20. A method as set forth in claim 18, further characterized in that aplurality of patterns are removed from a single piece of glass.
 21. Amethod as set forth in claim 20, further including the step of: a.creating additional vents between the patterns.
 22. A method as setforth in claim 21, further characterized in that said additional ventsare created by: a. applying nicks in one of the major surfaces of thepiece between the patterns, and b. heating said nicks to create ventsbetween the patterns.
 23. A method as set forth in claim 22, furthercharacterized in that said fracture is produced by the steps of: a.scoring a major surface of the piece in the form of the pattern, and b.propagating said score into a fracture that extends at least almostentirely to an opposite major surface of said piece.
 24. A method ofsevering a trim from a pattern in a piece of flat glass comprising thesteps of: a. scoring a major surface of said piece in the form of saidpattern, b. tapping said score from below to start a fracture, c.applying heat along said score from above to propagate said score into afracture that extends at least almost entirely to an opposite majorsurface of said piece, d. applying heat along said score from below, e.applying spot heat to a major surface of said trim adjacent to an edgeof said piece until a red glow appears, f. applying a mechanical defectto said edge of said piece adjacent to said red glow to complete a ventfrom said edge of said piece to said fracture, g. creating additionalvents in said trim until said trim is separated from said pattern, andh. seaming upper and lower portions of the pattern edge.
 25. A method ofsevering a trim from a pattern in a piece of flat glass comprising thesteps of: a. scoring a major surface of said piece in the form of saidpattern, b. tapping said score from below to start a fracture, c.applying heat along said score from above to propagate said score into afracture that extends at least almost entirely to an opposite majorsurface of said piece, d. applying heat along said score from below, e.applying a mechanicaL defect to said edge of said piece, f. heating saidtrim on a major surface thereof adjacent to said mechanical defect tocomplete a vent from said edge of said piece to said fracture, g.creating additional vents in said trim until said trim is separated fromsaid pattern, and h. seaming upper and lower portions of the patternedge.
 26. A method of severing a trim from a pattern in a piece of flatglass comprising the steps of: a. scoring a major surface of said piecein the form of said pattern, b. applying a top center tap at theapproximate center of curvature of said pattern to propagate the scoreinto a fracture, c. applying heat along the fracture from above tofurther propagate the fracture, d. applying heat from below along thefracture to further propagate the fracture, e. applying spot heat to amajor surface of said trim adjacent to an edge of said piece until a redglow appears, f. applying a mechanical defect to said edge of said pieceadjacent to said red glow to complete a vent from said edge of saidpiece to said fracture, g. creating additional vents in said trim untilsaid trim is separated from said pattern, and h. seaming upper and lowerportions of the pattern edge.
 27. A method of severing a trim from apattern in a piece of flat glass comprising the steps of: a. scoring amajor surface of said piece in the form of said pattern, b. applying atop center tap at the approximate center of curvature of said pattern topropagate the score into a fracture, c. applying heat along the fracturefrom above to further propagate the fracture, d. applying heat frombelow along the fracture to further propagate the fracture, e. applyinga mechanical defect to said edge of said piece, f. heating said trim ona major surface thereof adjacent to said mechanical defect to complete avent from said edge of said piece to said fracture, g. creatingadditional vents in said trim until said trim is separated from saidpattern, and h. seaming upper and lower portions of the pattern edge.